/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package jacky.lanlan.song.io.bit;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Utility code for dealing with different endian systems.
 * <p>
 * Different computer architectures adopt different conventions for byte
 * ordering. In so-called "Little Endian" architectures (eg Intel), the
 * low-order byte is stored in memory at the lowest address, and subsequent
 * bytes at higher addresses. For "Big Endian" architectures (eg Motorola), the
 * situation is reversed. This class helps you solve this incompatability.
 * <p>
 * Origin of code: Excalibur
 * 
 * @author <a href="mailto:peter@apache.org">Peter Donald</a>
 * @version $Id: EndianUtils.java 539638 2007-05-18 23:44:30Z bayard $
 * @see org.apache.commons.io.input.SwappedDataInputStream
 */
public abstract class EndianUtils {
	
	// ========================================== Swapping routines
	
	/**
	 * Converts a "short" value between endian systems.
	 * 
	 * @param value
	 *          value to convert
	 * @return the converted value
	 */
	public static short swapShort(short value) {
		return (short) ((((value >> 0) & 0xff) << 8) + (((value >> 8) & 0xff) << 0));
	}
	
	/**
	 * Converts a "int" value between endian systems.
	 * 
	 * @param value
	 *          value to convert
	 * @return the converted value
	 */
	public static int swapInteger(int value) {
		return (((value >> 0) & 0xff) << 24) + (((value >> 8) & 0xff) << 16) + (((value >> 16) & 0xff) << 8)
				+ (((value >> 24) & 0xff) << 0);
	}
	
	/**
	 * Converts a "long" value between endian systems.
	 * 
	 * @param value
	 *          value to convert
	 * @return the converted value
	 */
	public static long swapLong(long value) {
		return (((value >> 0) & 0xff) << 56) + (((value >> 8) & 0xff) << 48) + (((value >> 16) & 0xff) << 40)
				+ (((value >> 24) & 0xff) << 32) + (((value >> 32) & 0xff) << 24) + (((value >> 40) & 0xff) << 16)
				+ (((value >> 48) & 0xff) << 8) + (((value >> 56) & 0xff) << 0);
	}
	
	/**
	 * Converts a "float" value between endian systems.
	 * 
	 * @param value
	 *          value to convert
	 * @return the converted value
	 */
	public static float swapFloat(float value) {
		return Float.intBitsToFloat(swapInteger(Float.floatToIntBits(value)));
	}
	
	/**
	 * Converts a "double" value between endian systems.
	 * 
	 * @param value
	 *          value to convert
	 * @return the converted value
	 */
	public static double swapDouble(double value) {
		return Double.longBitsToDouble(swapLong(Double.doubleToLongBits(value)));
	}
	
	// ========================================== Swapping read/write routines
	
	/**
	 * Writes a "short" value to a byte array at a given offset. The value is
	 * converted to the opposed endian system while writing.
	 * 
	 * @param data
	 *          target byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @param value
	 *          value to write
	 */
	public static void writeSwappedShort(byte[] data, int offset, short value) {
		data[offset + 0] = (byte) ((value >> 0) & 0xff);
		data[offset + 1] = (byte) ((value >> 8) & 0xff);
	}
	
	/**
	 * Reads a "short" value from a byte array at a given offset. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static short readSwappedShort(byte[] data, int offset) {
		return (short) (((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8));
	}
	
	/**
	 * Reads an unsigned short (16-bit) value from a byte array at a given offset.
	 * The value is converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static int readSwappedUnsignedShort(byte[] data, int offset) {
		return (((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8));
	}
	
	/**
	 * Writes a "int" value to a byte array at a given offset. The value is
	 * converted to the opposed endian system while writing.
	 * 
	 * @param data
	 *          target byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @param value
	 *          value to write
	 */
	public static void writeSwappedInteger(byte[] data, int offset, int value) {
		data[offset + 0] = (byte) ((value >> 0) & 0xff);
		data[offset + 1] = (byte) ((value >> 8) & 0xff);
		data[offset + 2] = (byte) ((value >> 16) & 0xff);
		data[offset + 3] = (byte) ((value >> 24) & 0xff);
	}
	
	/**
	 * Reads a "int" value from a byte array at a given offset. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static int readSwappedInteger(byte[] data, int offset) {
		return (((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8) + ((data[offset + 2] & 0xff) << 16) + ((data[offset + 3] & 0xff) << 24));
	}
	
	/**
	 * Reads an unsigned integer (32-bit) value from a byte array at a given
	 * offset. The value is converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static long readSwappedUnsignedInteger(byte[] data, int offset) {
		long low = (((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8) + ((data[offset + 2] & 0xff) << 16));
		
		long high = data[offset + 3] & 0xff;
		
		return (high << 24) + (0xffffffffL & low);
	}
	
	/**
	 * Writes a "long" value to a byte array at a given offset. The value is
	 * converted to the opposed endian system while writing.
	 * 
	 * @param data
	 *          target byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @param value
	 *          value to write
	 */
	public static void writeSwappedLong(byte[] data, int offset, long value) {
		data[offset + 0] = (byte) ((value >> 0) & 0xff);
		data[offset + 1] = (byte) ((value >> 8) & 0xff);
		data[offset + 2] = (byte) ((value >> 16) & 0xff);
		data[offset + 3] = (byte) ((value >> 24) & 0xff);
		data[offset + 4] = (byte) ((value >> 32) & 0xff);
		data[offset + 5] = (byte) ((value >> 40) & 0xff);
		data[offset + 6] = (byte) ((value >> 48) & 0xff);
		data[offset + 7] = (byte) ((value >> 56) & 0xff);
	}
	
	/**
	 * Reads a "long" value from a byte array at a given offset. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static long readSwappedLong(byte[] data, int offset) {
		long low = ((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8) + ((data[offset + 2] & 0xff) << 16)
				+ ((data[offset + 3] & 0xff) << 24);
		long high = ((data[offset + 4] & 0xff) << 0) + ((data[offset + 5] & 0xff) << 8) + ((data[offset + 6] & 0xff) << 16)
				+ ((data[offset + 7] & 0xff) << 24);
		return (high << 32) + (0xffffffffL & low);
	}
	
	/**
	 * Writes a "float" value to a byte array at a given offset. The value is
	 * converted to the opposed endian system while writing.
	 * 
	 * @param data
	 *          target byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @param value
	 *          value to write
	 */
	public static void writeSwappedFloat(byte[] data, int offset, float value) {
		writeSwappedInteger(data, offset, Float.floatToIntBits(value));
	}
	
	/**
	 * Reads a "float" value from a byte array at a given offset. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static float readSwappedFloat(byte[] data, int offset) {
		return Float.intBitsToFloat(readSwappedInteger(data, offset));
	}
	
	/**
	 * Writes a "double" value to a byte array at a given offset. The value is
	 * converted to the opposed endian system while writing.
	 * 
	 * @param data
	 *          target byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @param value
	 *          value to write
	 */
	public static void writeSwappedDouble(byte[] data, int offset, double value) {
		writeSwappedLong(data, offset, Double.doubleToLongBits(value));
	}
	
	/**
	 * Reads a "double" value from a byte array at a given offset. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param data
	 *          source byte array
	 * @param offset
	 *          starting offset in the byte array
	 * @return the value read
	 */
	public static double readSwappedDouble(byte[] data, int offset) {
		return Double.longBitsToDouble(readSwappedLong(data, offset));
	}
	
	/**
	 * Writes a "short" value to an OutputStream. The value is converted to the
	 * opposed endian system while writing.
	 * 
	 * @param output
	 *          target OutputStream
	 * @param value
	 *          value to write
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static void writeSwappedShort(OutputStream output, short value) throws IOException {
		output.write((byte) ((value >> 0) & 0xff));
		output.write((byte) ((value >> 8) & 0xff));
	}
	
	/**
	 * Reads a "short" value from an InputStream. The value is converted to the
	 * opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static short readSwappedShort(InputStream input) throws IOException {
		return (short) (((read(input) & 0xff) << 0) + ((read(input) & 0xff) << 8));
	}
	
	/**
	 * Reads a unsigned short (16-bit) from an InputStream. The value is converted
	 * to the opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static int readSwappedUnsignedShort(InputStream input) throws IOException {
		int value1 = read(input);
		int value2 = read(input);
		
		return (((value1 & 0xff) << 0) + ((value2 & 0xff) << 8));
	}
	
	/**
	 * Writes a "int" value to an OutputStream. The value is converted to the
	 * opposed endian system while writing.
	 * 
	 * @param output
	 *          target OutputStream
	 * @param value
	 *          value to write
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static void writeSwappedInteger(OutputStream output, int value) throws IOException {
		output.write((byte) ((value >> 0) & 0xff));
		output.write((byte) ((value >> 8) & 0xff));
		output.write((byte) ((value >> 16) & 0xff));
		output.write((byte) ((value >> 24) & 0xff));
	}
	
	/**
	 * Reads a "int" value from an InputStream. The value is converted to the
	 * opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static int readSwappedInteger(InputStream input) throws IOException {
		int value1 = read(input);
		int value2 = read(input);
		int value3 = read(input);
		int value4 = read(input);
		
		return ((value1 & 0xff) << 0) + ((value2 & 0xff) << 8) + ((value3 & 0xff) << 16) + ((value4 & 0xff) << 24);
	}
	
	/**
	 * Reads a unsigned integer (32-bit) from an InputStream. The value is
	 * converted to the opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static long readSwappedUnsignedInteger(InputStream input) throws IOException {
		int value1 = read(input);
		int value2 = read(input);
		int value3 = read(input);
		int value4 = read(input);
		
		long low = (((value1 & 0xff) << 0) + ((value2 & 0xff) << 8) + ((value3 & 0xff) << 16));
		
		long high = value4 & 0xff;
		
		return (high << 24) + (0xffffffffL & low);
	}
	
	/**
	 * Writes a "long" value to an OutputStream. The value is converted to the
	 * opposed endian system while writing.
	 * 
	 * @param output
	 *          target OutputStream
	 * @param value
	 *          value to write
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static void writeSwappedLong(OutputStream output, long value) throws IOException {
		output.write((byte) ((value >> 0) & 0xff));
		output.write((byte) ((value >> 8) & 0xff));
		output.write((byte) ((value >> 16) & 0xff));
		output.write((byte) ((value >> 24) & 0xff));
		output.write((byte) ((value >> 32) & 0xff));
		output.write((byte) ((value >> 40) & 0xff));
		output.write((byte) ((value >> 48) & 0xff));
		output.write((byte) ((value >> 56) & 0xff));
	}
	
	/**
	 * Reads a "long" value from an InputStream. The value is converted to the
	 * opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static long readSwappedLong(InputStream input) throws IOException {
		byte[] bytes = new byte[8];
		for (int i = 0; i < 8; i++) {
			bytes[i] = (byte) read(input);
		}
		return readSwappedLong(bytes, 0);
	}
	
	/**
	 * Writes a "float" value to an OutputStream. The value is converted to the
	 * opposed endian system while writing.
	 * 
	 * @param output
	 *          target OutputStream
	 * @param value
	 *          value to write
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static void writeSwappedFloat(OutputStream output, float value) throws IOException {
		writeSwappedInteger(output, Float.floatToIntBits(value));
	}
	
	/**
	 * Reads a "float" value from an InputStream. The value is converted to the
	 * opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static float readSwappedFloat(InputStream input) throws IOException {
		return Float.intBitsToFloat(readSwappedInteger(input));
	}
	
	/**
	 * Writes a "double" value to an OutputStream. The value is converted to the
	 * opposed endian system while writing.
	 * 
	 * @param output
	 *          target OutputStream
	 * @param value
	 *          value to write
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static void writeSwappedDouble(OutputStream output, double value) throws IOException {
		writeSwappedLong(output, Double.doubleToLongBits(value));
	}
	
	/**
	 * Reads a "double" value from an InputStream. The value is converted to the
	 * opposed endian system while reading.
	 * 
	 * @param input
	 *          source InputStream
	 * @return the value just read
	 * @throws IOException
	 *           in case of an I/O problem
	 */
	public static double readSwappedDouble(InputStream input) throws IOException {
		return Double.longBitsToDouble(readSwappedLong(input));
	}
	
	/**
	 * Reads the next byte from the input stream.
	 * 
	 * @param input
	 *          the stream
	 * @return the byte
	 * @throws IOException
	 *           if the end of file is reached
	 */
	private static int read(InputStream input) throws IOException {
		int value = input.read();
		
		if (-1 == value) { throw new EOFException("Unexpected EOF reached"); }
		
		return value;
	}
}
